Norway, previously an international frontrunner concerning reductions of transboundary air pollution, fell far short of its 2010 target for nitrogen oxides (NOx) under the 1999 Gothenburg Protocol. In this article I show that leading international compliance theories cannot explain much of this noncompliance. While little evidence supports the management school’s explanations, Norwegian policies are also inconsistent with the enforcement school. Albeit too late to meet the deadline, Norway imposed a NOx tax in 2007. Moreover, the resulting emissions reductions were deeper than in a business-as-usual scenario, despite no international enforcement. That the NOx tax was imposed only after an environmentalist party gained considerable influence over NOx policies in 2005 supports an office-incumbent hypothesis. However, as emissions also declined significantly in many other European countries after 2005, the explanation is likely structural. One possibility is the deadline-pressure hypothesis: As the deadline approached, decision-makers across Northern and Western Europe considered emissions reductions to be more urgent than before.